<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .aaa{
            width: 50px;
            height: 50px;
            background-color: red;
            display: inline-block;
        }
    </style>
</head>
<body>
 <div style="text-align: center">
     <div class="aaa"></div>
 </div>
</body>
</html>